DESCRIPTION: The prediction of the structure of proteins based solely on their primary sequence, the design of denovo proteins with desired properties, and the refolding of proteins from inclusion bodies, all require a clear understanding of the principles underlying the formation and assembly of alpha-helices and beta-sheets. Progress has been made in establishing the propensity of each amino acid to form alpha-helices and also in the design of denovo alpha-helical peptides and proteins. However, the understanding of the formation of beta-sheets has been met with less success. The long term goal of Dr. Tasayco's research is to understand how protein structure governs function. The objective of this proposal is to understand the relationship among structure, stability, dynamics and folding of the still little understood beta-sheets using the association/folding process between complementary fragments of the mixed alpha beta thioredoxin protein as a model system. Understanding the folding of this structural motif, intrinsically important for the oxi-redox system, will provide the basis for the rational design of molecules with desired pharmacological properties. Dr. Tasayco's approach is to study four selected complementary protein fragments and compare them with the intact protein. She proposes to dissect E. coli thioredoxin into fragments. These fragments will be characterized using a combination of biochemical and biophysical tools with increasing level of structural detail. She will use circular dichroism in the far and near UV, fluorescence, multidimensional nuclear magnetic resonance spectroscopy and computer modeling. The work will be organized around three specific aims: Aim 1. Studies of the structure and stability of the isolated fragments (1-37, 38-73, 38-108, 74-108). Aim 2. Studies of the structure, stability and dynamics of non-covalent complexes (1-37 and 38-108, 1-37, 38-73 and 74-108). Aim 3. Comparison of the folding between the reconstituted and intact Trx.